Processes for recycling carpet and products of such processes

ABSTRACT

Methods for the recycling of carpet are disclosed that produce clean face fiber suitable for industrial use. The methods allow the recovery of face fiber material, for example a polyester or a polyamide, from carpets that includes a face fiber material and a backing material, and include the steps of heating the carpet to a temperature lower than the melting point of the face fiber material, but higher than the initial thermal decomposition temperature of the backing material, for a time and at a temperature sufficient to thermally decompose, pyrolyze, or oxidize at least a portion of the backing material, rendering the backing material friable, that is more friable than the untreated backing; and applying mechanical force to the carpet so as to liberate the friable backing material from the face fiber material.

FIELD OF THE INVENTION

The present invention relates to methods for carpet recycling, and morespecifically, to processes of recycling carpet that produce clean facefiber suitable for industrial use, and to the face fiber and otherproducts produced using such processes.

BACKGROUND OF THE INVENTION

A typical carpet is composed of four distinct materials: 1) the facefiber or pile, often made of nylon, polyethylene terephthalate, orpolyolefin; 2) the backing, often made of polypropylene or naturalfibers like jute; 3) the binder or adhesive, often a styrene butadienerubber (SBR) latex; and 4) the inorganic filler, often calcium carbonateor limestone. Thousands of tons of post-consumer and post-industrialcarpet are sent to landfills each year. These carpets are difficult torecycle, being mixtures of various plastics, binders, inorganic fillers,and fibers. Many high-end uses of recycled carpet require separating thedifferent polymers, removing dirt and other contaminants, and removingthe binders and other fillers. By design, carpeting is difficult todeconstruct. It is built to survive decades of wear without having theface fiber pull free from the backing material, and without the binderfailing.

The most valuable portion of the carpet is typically the “face fiber”material, also sometimes described as “pile,” which is often a polyesteror a nylon, and typically makes up from about 35 to about 65 wt.% of thecarpet. Carpet to be recycled is often sorted based on its face fibercomposition, with nylon carpet currently being more valuable due to thehigher demand for recycled nylon.

One conventional method for recovering the face fiber material typicallyinvolves shearing, a method for removing face fiber material analogousto shearing a sheep to remove its fleece. In such methods, the balanceis typically discarded. An advantage of this method is that most of thenon-face fiber portion of the carpet is separated from the face fiber. Adisadvantage of the method is that shearing is labor intensive. Piecesof carpet must be unrolled, cut into appropriately-sized pieces, andmanually fed one-by-one into a shearing unit. The carpet must be fedinto the shearer in the proper orientation, with the face fiber orientedtoward the shearing blades, making the sheared fiber susceptible tocontamination with the backing material. A further disadvantage of thismethod is that the yield of face fiber is low—typically only 25% to 50%of the face fiber is recovered.

In shearing, the cutting depth must be carefully adjusted to maximizeface fiber recovery while minimizing cutting into the backing material.Unfortunately, carpet thicknesses vary. Deep cuts risk contaminating thesheared fiber, while shallow cuts result in yield losses. Cutter wear insuch applications is significant and costly.

Another conventional method of carpet recycling is whole carpetshredding. The entire carpet is simply shredded into fibers, and aportion of the latex and inorganic filler are removed as sand or dust.However, this method has the disadvantage of leaving the backingpolypropylene fibers still intermixed with the face fibers. Furthermore,the bottom end of each face fiber retains a significant portion of thelatex and inorganic filler, making this face fiber unsuitable for usesthat require a more purified recycled face fiber.

U.S. Pat. No. 5,889,142 discloses a process for selectively separatingpolyamides from multi-component waste materials that includes the stepsof subjecting the multi-component mix to a specific mixture ofcaprolactam and water at a preselected temperature range below thedegradation temperature of the polymer to be recovered, separating theformed polyamide solution, and recovering the desired polyamide.

U.S. Pat. No. 7,067,613 discloses, in the recycling of Nylon 6 and Nylon6,6 polyamides from post-consumer or post-industrial waste, a process toseparate the polyamides from commingled polyolefin waste components,particularly polypropylene, by admixing the waste with an ester solventcomposition and heating the admixture to a temperature above the meltingtemperature of the contained polyolefins to form an ester solventcomposition further containing dissolved polyamide polymer and aseparate immiscible liquid polyolefin phase.

U.S. Pat. No. 6,752,336 discloses a method of recovering carpetmaterials by reducing carpet into size-reduced fibers, slurrying thesize-reduced fibers in a liquid medium, and then selectively separatingthe size-reduced fibers in a centrifuge. The method is said to beparticularly appropriate for recovering nylon or polyester face fibersfrom post-industrial, pre-consumer carpet waste.

U.S. Pat. No. 6,498,250 discloses a process for nylon depolymerizationin which a multi-component material, comprising nylon and one or morenon-nylon components, is fed to a depolymerization zone in whichdepolymerization of at least part of the nylon is effected, resulting ina product stream and a residue, the product stream containing monomersof the nylon, and the residue containing non-nylon components, in whichthe nylon content in the residue is measured and used to control thedepolymerization process.

U.S. Pat. No. 7,784,719 discloses methods of recovering primaryconstruction materials from whole carpet that are said to beparticularly appropriate for recovering nylon or polyester face fibersfrom post-industrial, post-consumer carpet waste. The methods includereducing the whole carpet into fragmented carpet materials (i.e., pile,backing, and binder), further reducing the fragmented carpet materialsinto size-reduced fibers and binder, slurrying the size-reduced fibersand binder in an aqueous liquid medium (e.g., water), and thenseparating the size-reduced fibers and binder in a centrifuge.

U.S. Pat. PubIn. No. 2011/0040027 discloses a method of recycling carpetcomponents that comprises converting post-consumer carpet that includesa latex backing into a free-flowing powder that is said to be suitablefor incorporation into one or more products as a recycled productcomponent. Various processes of converting post-consumer carpetcomprising a latex backing are disclosed, including a process in which aportion of face fibers may be harvested from used, post-consumer carpet,or the carpet may simply be shredded to form a first mixture, afterwhich a portion of carpet fibers are separated from and removed from thefirst mixture to form a second mixture, which may subsequently beexposed to a relatively high level of heat to thermally degrade and/orpartially volatilize polymeric material present in the second mixture.This mixture may then be incorporated into new products, either alone oradmixed with a solid inorganic particulate material.

Notwithstanding the carpet recycling methods just described, thereremains a need in the art for improved processes for recycling carpet,especially those containing face fibers such as nylons and polyesters.

SUMMARY OF THE INVENTION

In one aspect, the invention relates to processes for recovering facefiber material from a carpet that includes a face fiber material and abacking material, the processes include the steps of heating the carpetto a temperature lower than the melting point of the face fibermaterial, but higher than the thermal decomposition temperature of thebacking material, for a time and at a temperature sufficient todecompose at least a portion of the backing material, rendering thebacking material more friable than in its original state; and applyingmechanical force to the carpet so as to liberate the friable backingmaterial from the face fiber material. These steps may be carried outsequentially or simultaneously, so long as the backing material has beenrendered sufficiently friable so as to be separable from the face fibermaterial. Similarly, the steps may be carried out in separateapparatuses or in the same apparatus, so long as the apparatus includesa means of heating the carpet and a means to apply mechanical force tothe carpet so as to liberate the friable backing material from the fibermaterial. The steps can be carried out batch wise or continuously.

In another aspect, the invention relates to the face fiber materialobtained from these processes, which is largely free of polypropylene,adhesive, and inorganic filler.

In a further aspect, the invention relates to friable backing materialobtained from such processes, also called backing residue, which willtypically constitute a backing material, and an adhesive such as a latexfilled with an inorganic filler.

In a further aspect, the invention relates to inorganic filler obtainedfrom these processes, which has uses, for example, in the backing of newcarpet, pH adjustment of fluids, and coal desulfurization.

Further aspects of the invention are as disclosed and claimed herein.

DETAILED DESCRIPTION

Thus, in one aspect, the invention relates to a process that includes astep of heating a carpet that includes a face fiber material and abacking material, so as to render at least a portion of the backingmaterial friable, that is, more friable than the untreated backing, suchas by thermal decomposition. As used herein, the terms “thermaldecomposition,” “decompose,” and the like are intended to includepyrolysis and/or oxidation reactions. Such thermal decompositions takeplace over a broad temperature range, and for purposes of the invention,the carpet or entangled fiber is heated to at least the “initial”thermal decomposition temperature, that is, the temperature at which thebacking material begins decomposing. For this invention, the temperatureat which thermal decomposition commences is less than the meltingtemperature of the face fiber.

The friable backing material, and optionally any other carpet componentssuch as adhesive and inorganic filler, may then be freed from attachmentto the face fibers, for example by simultaneously reducing the particlesize of the friable components while freeing them from attachment to theface fibers. The heating step and the liberation step may be carried outsequentially, or simultaneously, so long as the backing material hasbeen rendered sufficiently friable so as to be separable from the facefiber material.

The methods of the invention may be used to liberate the backingmaterial from the face fiber material of any carpet in which the backingmaterial may be preferentially thermally decomposed (or pyrolyzed and/oroxidized, as above) with respect to the face fibers, for example withany carpet in which the backing material decomposes at a lowertemperature than the melting point or the decomposition point of theface fiber material. The greater the difference between the temperaturesat which the two materials thermally decompose, the more satisfactorywill be the subsequent separation.

The processes of the invention are best carried out in those cases inwhich the face fiber material does not melt at the temperature at whichthe backing material initially begins to decompose, although somemelting may still be tolerated if a lower yield of face fiber materialis acceptable. It may also be possible to preferentially heat thebacking material so that the face fiber material does not substantiallymelt, and still recover the face fiber material from the backingmaterial rendered friable, although it will be understood that thegreater the difference in thermal decomposition temperature between thebacking material and the face fiber material, the more satisfactory willbe the subsequent separation according to the processes of theinvention.

As used herein, the term “carpet” is intended to be interpreted broadlyto describe a decorative or protective multi-component material thatincludes a backing material, a face fiber material typically comprisedof a plurality of fibers, and optionally an inorganic filler, typicallycombined with an adhesive, which itself has industrial uses onceseparated from the other carpet components. In one aspect, the facefiber material may comprise, for example, a nylon or a polyester, thebacking material a woven polypropylene, and the adhesive an inorganicfilled latex.

The types of carpet useful according to the invention include newcarpet, post- industrial carpet, or post-consumer carpet. As usedherein, the term “carpet” also includes the residue from carpet shearingprocesses, often referred to as “carpet carcass”. This comprises backingmaterial with the residual fiber that remains attached after mechanicalshearing.

As used herein, the term “carpet” is also intended to include fibrousmaterial comprised of two or more different types of fibers in which onetype of fiber has a lower thermal decomposition or oxidation orpyrolysis temperature than the other. One example of such a material istrunk liner mat, which is comprised of non-woven PET fiber, which may beconsidered the face fiber material, and a polyolefin binder, which maybe considered the backing material. Another example is carpet paddingmade from recycled carpet which may be comprised of PET or nylon fiber,and/or polypropylene fiber, and one or more backing components andadhesives.

According to the invention, the backing material, which is typically awoven material, comprises a material that may be thermally decomposed,pyrolyzed, or oxidized, for example a polyolefin such as polyethylene orpolypropylene. The backing material may further comprise additionalmaterials such as adhesives and inorganic fillers, as further describedherein, which together form a friable backing material or a backingresidue when the carpet is heated according to the invention, as furtherdescribed herein.

The face fiber material may comprise, for example, a nylon or apolyester, or a mixture of nylons, or a mixture of polyesters, or amixture of nylons and polyesters, which preferably melts at atemperature higher than the thermal decomposition temperature of thebacking material. Nylons are, of course, also known as polyamides, andthe terms are used herein interchangeably to describe polymers comprisedof repeating units joined by amide groups, including without limitationnylon-6 and nylon-6,6. Polyesters amenable to separation according tothe invention are polymers having repeating ester linkages and includepolyethylene terephthalate (PET) homopolymers and copolymers,polybutylene terephthalate (PBT) homopolymers and copolymers, and thelike, including those that contain comonomers such ascyclohexanedimethanol, cyclohexanedicarboxylic acid, and the like.

In carpet, the face fiber material is typically oriented with respect tothe backing material in a U-shape, in which a fiber is inserted into thebacking material and forms a U, with the middle of the fiber in contactwith the backing material, and the fiber either cut to a uniform length,called plush pile, or left uncut, so-called loop pile. Piles of eitherform are described herein as face fibers, and are suitably separatedfrom the backing material by the processes according to the invention.

Carpets are thus typically formed by the face fiber being anchored intoa web of backing material, for example polypropylene threads, that areflexible at ambient temperature. Carpets useful for the inventiveprocess may also include in the backing material an adhesive such as alatex, for example an SBR (styrene/butadiene/rubber) latex, filled withan inorganic substance such as calcium carbonate as an inorganic filler,provided to add weight to the carpet, with the adhesive helping tomaintain the face fiber material attached to the backing material. Thecarpets may further comprise a polypropylene net material in contactwith the adhesive material, also intended to ensure that the face fibersdo not inadvertently separate from the backing material during use.

Indeed, it is the presence of these various materials intended tomaintain the integrity of the carpet during use that make the subsequentseparation of the face fibers from the backing material so difficult inpractice. It is the preferential thermal decomposition of the backingmaterial, and optionally any adhesive material and polypropylenenetting, that assists in obtaining the usable face fiber materialaccording to the invention.

As used herein, the term “friable” means that the material has beenrendered more easily cut, ripped, torn, shredded, crumbled orpulverized, and is to be distinguished from the thermoplastic, orelastic, or flexible state of the backing material of the carpet such aswould be the case, for example, of polyolefin threads provided as thebacking material for the carpets during use. It is understood that theterm “friable” should be interpreted broadly so as to cover any state inwhich a previously flexible backing material for a carpet is renderedmore easily liberated and separated from the flexible face fibermaterial due to an increased tendency to crumble or pulverize due to atleast a partial thermal decomposition and/or oxidation and/or pyrolysisof the backing material.

Thus, in one aspect, the invention relates to processes for recoveringface fiber material from a carpet that includes a face fiber materialand a backing material, the process comprising: a) heating the carpet toa temperature lower than the melting point of the face fiber material,but higher than the thermal decomposition temperature of the backingmaterial, for a time and at a temperature sufficient to thermallydecompose at least a portion of the backing material, rendering thebacking material friable; and b) applying mechanical force to the carpetso as to liberate the face fiber material from the friable backingmaterial. The carpet may be heated in step a) to a temperature, forexample, from about 175° C. to about 260° C.

When the face fiber material comprises nylon 6, for example, the carpetmay be heated in step a) to a temperature from 175° C. to 215° C. Whenthe face fiber material comprises nylon 6,6, for example, the carpet maybe heated in step a) to a temperature, for example, from 175° C. to 245°C. When the face fiber material comprises polyethylene terephthalate,for example, the carpet may be heated in step a) to a temperature from175° C. to 260° C.

According to the invention, the carpet may be heated in step a) for atime, for example, from about 0.1 minutes to about 120 minutes.

In one aspect, steps a) and b) may be carried out in the same apparatus.In other aspects, steps a) and b) may be carried out sequentially, orsimultaneously, and may be carried out in a batch process, or may becarried out in a continuous process.

In the processes according to the invention, the carpet may be cooledbetween steps a) and b), thereby causing at least a portion of thebacking material to spontaneously fracture.

As used herein, the face fiber material may comprise a polyester, or anylon (a polyamide), or both a nylon and a polyester, and the backingmaterial may independently comprise a polyolefin, or a natural fiber,such as jute.

The invention further comprises the face fiber material recoveredaccording to the processes of the invention. This face fiber materialmay be in the form of a fiber, or may be extruded to form an article, ormay be injection-molded to form an article.

In a further aspect, the invention relates to the use of the face fibermaterial obtained according to the invention in one or more chemicalrecycling processes.

The process of the invention may further comprise separating anyinorganic filler from the friable backing material, and the inventionrelates as well to the inorganic filler so obtained.

In yet another aspect, the invention relates to processes for recoveringface fiber material from a carpet that includes a face fiber materialand a backing material of different chemical composition than the facefiber material, the process comprising: a) heating the carpet to atemperature lower than the melting point of the face fiber material, buthigher than the initial thermal decomposition temperature of the backingmaterial, for a time and at a temperature sufficient to thermallydecompose and/or oxidize at least a portion of the backing material,rendering the backing material more friable than the untreated backing;b) applying mechanical force to the carpet so as to liberate the facefiber material from the friable backing material; and c) removing anycontaminants from the face fiber material through one or more mechanicalmeans.

In another aspect, the invention relates to the friable backing materialso obtained, and to a desulfurization agent comprising the friablebacking material so obtained.

And in a further aspect, the invention relates to methods of separatingat least a first type and a second type of fiber that are entangled, theprocess comprising: a) heating the entangled fibers to a temperaturelower than the melting point of the first type of fiber, but higher thanthe thermal decomposition temperature of the second type of fiber, for atime and at a temperature sufficient to thermally decompose at least aportion of the second type of fiber, rendering the fibers of the secondtype of fiber friable; and b) applying mechanical force to the entangledfibers so as to liberate the first type of fiber from the friable secondtype of fiber.

In one aspect, then, the invention relates to a process that includes astep of heating a carpet comprised of at least a face fiber material anda backing material to a temperature lower than the melting point of theface fiber material, but higher than the initial thermal decompositiontemperature of at least a portion of the backing material, for a timeand at a temperature sufficient to thermally decompose at least aportion of the backing material, rendering it friable, that is, morefriable than the untreated backing. The friable component(s) may then beliberated from attachment to the face fibers, for example bysimultaneously reducing the particle size of the friable componentswhile freeing them from attachment to the face fibers. This is to bedistinguished from a case in which all of the polymeric material in thecarpet (both face fiber and backing) is rendered friable or thermallydecomposed, or a case in which the polymeric material is simply meltedand blended to serve, for example, as composite material for uses inwhich the physicochemical properties of the resulting blend are notparticularly demanding. This is also to be distinguished from a processin which the polymeric material is entirely thermally degraded, leavingonly an inorganic residue. According to the present invention, thepolymeric face fiber material is liberated and separated from thebacking material in a form in which it may be used with relativelylittle further processing required.

In the processes of the invention, the temperature to which the carpetis heated may vary, for example, depending upon the nature of the facefiber material and the backing material. For example, the temperaturemay be at least about 175° C., or at least 190° C., or at least 200° C.,up to about 235° C., or up to 245° C., or up to 250° C.

When the face fiber material comprises a polyester, for example apolyethylene terephthalate having a melting point from about 250° C. toabout 260° C., the carpet may be heated to a temperature from about 175°C. to about 250° C., or from 180° C. to 245° C.

When the face fiber material comprises a nylon, for example nylon 6,6having a melting point from about 240° C. to about 250° C., the carpetmay be heated to a temperature from about 175° C. to about 240° C., orfrom 180° C. to 235° C.

When the face fiber material comprises a nylon, for example nylon 6having a melting point from about 215° C. to about 220 ° C., the carpetmay be heated to a temperature from about 175° C. to about 215° C., orfrom 180° C. to 210° C.

When the backing material comprises a polypropylene that beginsthermally decomposing at a temperature of about 175° C., the carpet maybe heated to a temperature greater than 175° C. and less than themelting point of the face fiber.

The length of time during which the carpet will be heated will varydepending upon the temperature to which the carpet is heated as well asthe composition of the backing material and the face fiber material, andmay be for a time of at least about 0.1 minutes, or at least 2 minutes,or at least 3 minutes, or at least 5 minutes, up to about 120 minutes,or up to 60 minutes, or up to 30 minutes, or up to 10 minutes, or up to5 minutes.

In one aspect, the carpet fed to the processes according to theinvention may be provided as an entire bale of carpet shredded to a sizesuitable for easy handling. Shredded feed suitable for this process canrange in top size from as small as 0.5 cm square to as large as 1 metersquare. This shredding can occur in any type of commercial shredder orgranulator, or can occur in a device such as a step cleaner or cottongin or carding unit. Alternatively, the carpet may be used in a form inwhich no preparatory shredding or cutting is done, other than minimalcutting necessary to fit the carpet into the heating source.

According to the invention, after preparatory shredding, any ferrouscontamination may be removed, for example, by magnetic separation. Finesmay likewise be removed, although this too may not be required. We notethat finer shredding, if used, will generate more fines. The shreddedcarpet may optionally be granulated and screened to obtain a relativelysmall particle size distribution. However, pieces of carpet at least 0.5square inches, and more preferably 1 square inch, and more preferably 2or more square inches appears to be suitable for this process.

The carpet may then be heated for a time and to a temperature sufficientto cause at least a portion of the backing material to thermally degradeand/or oxidize, becoming more friable upon cooling. As noted, thetemperature to which the carpet is heated is preferably below themelting point of the face fiber material, but sufficiently high to causethermal decomposition or oxidation of at least a portion of the backingmaterial, which may include other non-face fiber organics or inorganicspresent in the carpet. However, the temperature of the environment towhich the carpet is exposed in the heating device may be in excess ofthe melting point of the face fiber, since the carpet will require sometime in the heating device for the actual carpet temperature to increasefrom ambient to a higher temperature.

The melting range of polyethylene terephthalate, for example, is about250° C. to about 260° C. Useful conditions for polyester carpet, asfurther described elsewhere herein, are from about 175° C. to about 245°C., and for a length of time, for example, from about 0.1 to about 120minutes.

The desired temperature for nylon 6,6 carpet may be slightly lower,since the nylon melting range is from about 245° C. to about 250° C.Useful temperatures for nylon 6,6 as further described elsewhere herein,are from about 175° C. to about 240° C., and for a length of time, forexample, from about 0.1 to about 120 minutes.

The desired temperature for nylon 6 carpet may be slightly lower still,since the nylon melting range is from about 215° C. to about 220° C.Useful conditions for nylon 6 as further described elsewhere herein, arefrom about 175° C. to about 215° C. and for a length of time, forexample, from about 0.1 to about 120 minutes.

Typically, the non-face fiber portions of the carpet will turn tan,brown, or black, and some vapors may be emitted from the decomposing oroxidizing organics.

An additional advantage of this invention is that through the heatingportion of the process, many of the malodorous and/or pathogeniccontaminants found in used carpet are vaporized, oxidized, pyrolyzed,carbonized, or otherwise destroyed. These would include items such asfood and drink residues, bodily fluids, fecal matter, bacteria, vermin,etc. Such removal renders the face fiber from this process much cleanerand more hygienic than that derived by simple shearing.

As noted, the time and temperature needed to render at least a portionof the backing material friable will be a function of the composition ofthe carpet, and especially the composition of the face fiber materialand the backing material, the rate of heat transfer in the heatingdevice, and the size of the carpet piece being heated, and may be easilydetermined by one skilled in the art using routine experimentation. Thecarpet may thereafter be sufficiently cooled to solidify any melted ordecomposed or oxidized portions, thus rendering them at least partiallyfriable. The cooling applied may be wet or dry.

Once at least a portion of the backing material of the shredded carpethas been rendered friable, the friable portion of the carpet may beliberated from the face fibers, for example by being mechanicallyreduced to a smaller particle size by crushing or milling, for exampleusing hammer milling, ball milling, rod milling, dual roll crushers, pinmilling, single shaft shredders, dual shaft shredders, quad shaftshredders, granulators, carders, fiber combs, fiber “gins”, autogenicgrinding mills, fiber cleaners or any other device or combinations ofdevices capable of liberating the backing material from the face fibermaterial, such as by crushing the friable particles to a smaller size.We note that such devices do not typically significantly reduce the sizeof the face fiber material, for example the polyester or nylon fiber,since the fiber material remains substantially flexible, and notfriable. This size reduction step can also serve to at least partiallyseparate the liberated backing material from the face fiber. Thiscrushing or milling also serves to liberate the agglomerates of friablematerial from the polyester or nylon fibers to which it was attached.

The contaminants may then be further separated from the face fiber, byany number of suitable wet or dry methods, for example by screening,aspiration, carding, combing, other mechanical fiber cleaners, waterwashing, air washing, or combinations of these methods.

We note that the heating step may be carried out simultaneously with themilling, for example in a ball mill provided with heated balls for thispurpose.

Similarly, in certain devices such as in an “air swept” continuous ballmill, or in an “air swept” carding type unit, the liberating and theseparating steps can be carried out simultaneously.

The face fibers may thereafter optionally be further washed, cleaned,combed or carded to further reduce attached contaminants usingtechniques known to those skilled in the art of fiber cleaning. Afloat/sink separation may optionally be provided to further reducecontaminants, thus capitalizing on the greater specific gravity of thedecomposed contaminants vs. the specific gravity of the face fiber.Froth flotation may likewise optionally be used to further reducecontaminants, thus capitalizing on the much higher surface-to-volumeratio of the face fibers compared with that of the crushed contaminants.The cleaned fibers may thereafter optionally be formed into granules orpellets either by melting in a unit such as an extruder with an attachedpelletizer or a Condux type densifier or by compression in a unit suchas a California Pellet Mill, for easier handling and storage.Alternatively the fibers may be used as is, for example for chemicalrecycling or extrusion or injection molding.

In yet another embodiment, the carpet may be used as provided, withoutany further shedding or cutting, other than what might be necessary inorder for the carpet to fit within the heat source selected. In thisaspect, the carpet may be fed into or through an oven by any suitablemeans of conveyance.

A variety of heat sources may be used according to the invention,whether conventional natural convection ovens, forced convection ovens,microwave ovens, infrared ovens, or the like. Additional heating sourcesinclude rotary kilns, laser beams, heated rollers, heated solids, heatedfluids, heated gases, and superheated steam. The heating can be director indirect. The heat source may be provided in such a way that heat ispreferentially supplied to the backing material, or it may be applied tothe entire piece of carpet.

As noted, the maximum temperature to which the carpet is raised willtypically be less than the melting temperature of the face fibermaterial, that is, a temperature at which the face fibers do notsubstantially melt, yet at a temperature sufficiently high so as to atleast partially decompose the backing material, that is, a temperatureat which at least a portion of the backing material begins to decompose.Ideally, at least the portion of the backing material in contact with oradjacent to the face fiber material will thermally decompose and/oroxidize, so that the face fiber material may thereafter be adequatelyliberated from the friable backing material.

When the backing material is polypropylene, for example, the carpet maybe treated at a temperature of at least 175° C., or at least 180° C., orat least 190° C., in order to render the backing material at leastpartially friable, or at least a portion of the backing materialfriable. When the face fiber material is polyethylene terephthalate, thecarpet will typically be heated to a temperature no higher than 250° C.,or no higher than 245° C., or no higher than 243° C., so as to avoidsubstantial melting of the face fiber material.

To further elaborate, in one aspect, the process is carried out byshredding a part or even an entire bale of carpet to a size suitable foreasy handling. We note that it is not necessary to remove any balingwire prior to the shredding, since any wire pieces may be removedmagnetically after shredding.

The shredding may be carried out in a variety of manners, for exampleusing a twin-shaft shredder such as those made by SSI or Shred Tech, ora single-shaft shredder such as those made by Linder or Komptech or agranulator such as those made by Cumberland or Rapid, or a cardingmachine or a “cat's claw,” such as those made by Southern Mechatronicsor Laroche.

The shred size may, if desired, be less than one meter square, or lessthan one decimeter square, or less than 1 centimeter square or less than0.5 cemtimeters square.

Any ferrous contamination may be removed, for example, by magneticseparation of nails, staples, other ferrous contaminants, and the like.Non ferrous metallic contaminants can be removed, for example, by eddycurrent machines.

Fines may optionally be removed at this point, if desired, usingscreening, aspiration, or any other suitable means to remove fines fromthe shredded material. The fines will typically be rich in calciumcarbonate from the backing, as already described, and finer shreddingwill, of course, generate more fines.

The shredded carpet may optionally be granulated to an even smallerparticle size distribution, for example by a granulator such as thosemade by Cumberland or Herbold. These granulators contain a screen thatlimits the size of the largest particles passing through the unit. Sucha granulator screen, if used, may have holes, for example, that are lessthan 2 inches in diameter, or less than 1 inch in diameter. The sizedesired may be selected in order to maximize liberation of the facefiber material while minimizing chopping of the face fiber. Contaminantsmay optionally be removed post-granulation, for example by magneticseparation of ferrous contaminants, eddy current separation ofnon-magnetic metals, and/or screening and/or aspiration for removal offines which, again, are typically rich in calcium carbonate from thecarpet backing.

The chopped carpet is then heated at a sufficient time and to atemperature to cause the non-face-fiber material components to becomefriable upon cooling, but below the melting point of the face fibermaterial. The temperature must, of course, nonetheless be sufficient tocause thermal decomposition of at least a portion of the backingmaterial of the carpet.

The heating of the carpet according to the invention may be carried outin a variety of manners, whether in a batch or a continuous manner, andusing a variety of heat sources.

In one aspect, the heating of the carpet may be carried out in batchmode, in which carpet is placed within or on a heat source, such as anoven or heated enclosed space.

In another aspect, the heating of the carpet may be carried outcontinuously, in which the carpet is conveyed upon or within a varietyof heat sources, such as ovens equipped with a moveable conveyor, rotarykilns, heated rollers, pneumatic transport devices equipped with airheaters, etc. The carpet pieces may remain in the same orientation inwhich they were fed into the device, or they may be turned or tumbled ormixed as they pass through the heating device. The turning may beaccomplished by mechanical means or by gas jets or by other means.Tumbling of the pieces may be accomplished by having one conveyor beltdischarge onto another conveyor belt or by creating an “S” bend in asingle conveyor belt. Heating and mixing can occur simultaneously in aheated pug mill or screw conveyor. Heating sources suitable for practiceof the invention may thus include a static oven, a rotary kiln, or anoven with a moving belt. The heating of the carpet may occur in air,that is, no special atmosphere is required. Alternatively, the heatingmay be carried out in an atmosphere selected so as to minimize theformation of oxidation products, leading to increased pyrolysisreactions and pyrolysis products.

The heating can be carried out in the presence of oxygen, since one modeof thermal decomposition of the backing material is an oxidativeprocess, in which oxygen is beneficial so as to render the desiredfriability. Such heating can be carried out in normal air, or inoxygen-depleted air such as that found in recirculated flue gas.

The carpet can be oriented in the heating devices in a number of ways.On a moving conveyor belt, for example, the carpet may be loaded pileside up or pile side down. The carpet pieces may overlap or be stackedone upon the other. Stacked or overlapped pieces may be orientedpile-to-pile or pile-to-backing. If the carpet is passed over a singleheated roller, the carpet could be oriented with the pile towards theheated roller or away from the heated roller, although orientation ofthe backing towards the heated roller may be preferable. If the carpetis passed between two heated rollers, then orientation is irrelevant,since one roller will always be in contact with the backing. If thecarpet pieces are heated in a device such a rotary kiln that tumbles thepieces or if the carpet pieces are heated in a device that stirs ormixed the pieces, then no orientation of the carpet pieces is possibleor required.

We note that typically, when the face fiber material is polyethyleneterephthalate, nylon, or the like, the non-face fiber portions of thecarpet will turn beige, tan, brown, or black, and some vapors or smokemay be emitted from the decomposing organic materials present. Theactual time and temperature selected, as already noted, will be afunction of the composition of the carpet, and especially thecomposition of the face fiber material and the backing material. Othermaterials such as latex or other types of adhesive and the like may alsobe present, typically filled with an inorganic filler, and thetemperature may be selected so as to also render friable theseadditional materials. Any adhesive and/or inorganic filler remaining maybe separated from the face fiber material using any suitable means, asdescribed elsewhere herein. A suitable temperature may be selected bythose skilled in the art based on the components of the carpet, and thetime and temperature may likewise be varied as the source of the carpetchanges, in order to obtain a suitable separation of the backingmaterial and other components from the face fiber material.

The carpet is, of course, subsequently cooled sufficiently so as tosolidify at least a part of the melted portions of the backing material,rendering them more friable. A variety of types of cooling may beacceptable, whether wet or dry. These would include air, humidified air,water mist, or liquid water. Indirect cooling methods such as chilledrollers could also be useful. Heat exchange devices may be utilized torecover waste heat.

If the subsequent size reduction step will include wet granulation orthe like, then the hot carpet may be dropped directly into liquid waterand pumped to the size reduction apparatus.

After cooling, the face fiber material is liberated from the friablebacking material by any suitable method, for example by mechanicallyreducing the size of the friable portion of the chopped carpet to anaverage particle size smaller than that at which they entered the step.Options include hammer milling, ball milling, rod milling, dual rollcrushers, pin mills, single shaft shredders, dual shaft shredders, quadshaft shredders, granulators, carders, fiber combs, fiber “gins”, stepcleaners, air classifiers, autogenic grinding mills, fiber cleaners, orany other device capable of reducing the friable particles to a smallersize and liberating them from the face fiber.

We note that such devices will typically not significantly reduce thesize of the face fiber material, because the temperature to which thecarpet is heated is selected so that the face fiber material remainssubstantially flexible and not friable. We note that the size reductionstep just described also serves to liberate the agglomerates of friablebacking material from the face fiber material to which it was attached.The contaminants may then be separated from the face fiber materialusing any suitable method, for example a wet or dry method such asscreening, aspiration, combing, carding, water washing, or air washing.Alternatively, in a device such as an air swept continuous ball mill,the milling and separation steps may be carried out simultaneously.

The resulting face fiber material may optionally be combed or carded tofurther reduce any attached contaminants, as is done to remove burrs,seeds, etc. from natural fibers. An optional float/sink separationtechnique may be used to further reduce contaminants, thus capitalizingon the greater specific gravity of the decomposed contaminants vs. thespecific gravity of the face fiber material. A froth flotation mayoptionally be used to further reduce contaminants, capitalizing on themuch higher surface-to-volume ratio of the face fiber material comparedwith that of the crushed contaminants, for example using micro airbubbles to cause the face fiber to float in water while the contaminantssink.

Further, the face fiber may optionally be pelletized for easy handlingand storage, via an extrusion and pelletizing operation, for examplewith a Gala underwater pelletizer, or compression pelletized for exampleusing a California pellet mill. The face fiber could be agglomerated ina unit such as a Condux agglomerator or a tub densifier. The face fibercould be baled or boxed.

As will be readily appreciated from the foregoing, advantages of theinvention include higher recovery of face fiber compared to shearing;higher quality of face fiber compared to simple shredding; low manpower;the use of whole, unopened bales; avoidance of extensive manual cuttingof the carpet; avoiding shearing and insertion of the carpet in aspecific orientation; lower operating cost; and the like.

The invention further relates to face fiber material liberated accordingto the invention, which face fiber material may have a variety of uses,including as a reactant in a chemical recycling process, for examplealcoholysis, glycolysis or ammonolysis, or use as-is as a fibrousmaterial, or further reacted to increase the molecular weight of thenylon or the polyester, as the case may be.

Any remaining backing residue may also find use in a number ofapplications. Typically the friable backing material, or generally thebacking residue, once separated from the face fiber material, willcomprise an inorganic filler rich in calcium carbonate and will have anominal BTU value of approximately 3,000 BTUs per pound. The backingresidue may, for example, be blended with coal to provide sulfur captureand heating value. The backing residue, and especially the inorganicfiller, may also be sized and re-used in new carpet as an “inert filler”in the latex or other adhesive. The inorganic filler of the backingresidue may also find use in adjusting the pH of various fluids.

EXAMPLES Comparative Example 1

Nylon carpet was shredded and sieved to remove granules of backing fromthe face fiber. Yield of fiber was about 50% of the feed to the process.The composition of the face fiber product was 75% nylon, 18%polypropylene, and 7% ash.

Comparative Example 2

Nylon carpet was sheared to remove the face fiber, leaving behind acarcass that comprised the backing and a portion of the face fiber. Theyield of face fiber was about 23 wt% of the feed to the process, and theface fiber contained about 2 wt% ash.

Example 1

A sample of nylon carpet was passed through a convection oven held at410° F. with a total residence time of 5 to 10 minutes to partiallydecompose the carpet backing. The oven product was then hammer milled toliberate the backing residue from the face fiber. Face fiber wasseparated from the bulk of the backing residue by screening. The fiberwas then further cleaned by carding. The yield of face fiber was about43 wt%, and the fiber was analyzed at 98% nylon. The residual materialin the fiber consisted of additional granules of decomposed backing thatcould have been removed by further carding.

Example 2

A sample of PET carpet was passed through a convection oven held at 455°F. with a total residence time of 5 minutes to partially decompose thecarpet backing material. The oven product was then hammer milled toliberate the backing residue from the face fiber. Face fiber wasseparated from the bulk of the backing residue by screening. The fiberwas then further cleaned by carding. The yield of face fiber was about67 wt%, and the fiber was analyzed at 96% PET. The residual material inthe fiber consisted of additional granules of decomposed backing thatcould have been removed by further carding.

Example 3

Another sample of PET carpet was passed through a convection oven heldat 410° F. with a total residence time of 10 minutes to partiallydecompose the carpet backing. The oven product was then hammer milled toliberate the backing residue from the face fiber. Face fiber wasseparated from the bulk of the backing residue by screening. The fiberwas then further cleaned by carding. The yield of face fiber was about62 wt% and the fiber was analyzed as 92% PET.

Example 4

Another sample of PET carpet was heated in a batch oven held at 410° F.with a total residence time of 30 minutes to partially decompose thecarpet backing. The oven product was then ball milled to liberate thebacking residue from the face fiber. Face fiber was separated from thebulk of the backing residue by screening. The yield of face fiber wasabout 55 wt%.

Example 5

PET carpet was heated in a batch oven held at 420° F. with a totalresidence time of 10 minutes to partially decompose the carpet backing.The oven product was then size reduced in a three bladed single shaftgranulator to liberate the backing residue from the face fiber. Facefiber was separated from the bulk of the backing residue by screening.The yield of face fiber was about 50 wt%.

Example 6

A sample of Nylon carpet was heated in a batch oven held at 410° F. witha total residence time of 25 minutes to partially decompose the carpetbacking. The oven product was then size reduced using a two-roll mill toliberate the backing residue from the face fiber. Face fiber wasseparated from the bulk of the backing residue by screening andaspirating. The yield of face fiber was about 52 wt%.

Example 7

Another sample of PET carpet was heated in a batch oven held at 480° F.with a total residence time of 3 minutes to partially decompose thecarpet backing. The oven product was then size reduced using a ball millto liberate the backing residue from the face fiber. Face fiber wasseparated from the bulk of the backing residue by screening andaspirating. The yield of face fiber was about 58 wt%.

Example 8

Another sample of PET carpet was heated in a batch oven held at 440° F.with a total residence time of 6 minutes to partially decompose thecarpet backing. The oven product was then size reduced using a ball millto liberate the backing residue from the face fiber. Face fiber wasseparated from the bulk of the backing residue by screening andaspirating. The yield of face fiber was about 64 wt%.

Example 9

PET carpet with jute backing was passed through a convection oven heldat 455° F. with a total residence time of 5 minutes to partiallydecompose the carpet backing. The oven product was then hammer milled toliberate the backing residue from the face fiber. Face fiber wasseparated from the bulk of the backing residue by screening. The fiberwas then further cleaned by carding. The yield of face fiber was about63 wt%, and the fiber was analyzed at 94% PET. The residual material inthe fiber consisted of additional granules of decomposed backing thatcould have been removed by further carding.

Example 10

Another sample of PET carpet with Shaw “soft back” was passed through aconvection oven held at 455° F. with a total residence time of 10minutes to partially decompose the carpet backing. The oven product wasthen ball milled to liberate the backing residue from the face fiber.Face fiber was separated from the bulk of the backing residue byscreening. The yield of face fiber was about 58 wt%.

Example 11

A sample of Nylon carpet carcass was heated in a batch oven held at 410°F. with a total residence time of 10 minutes to partially decompose thecarpet backing. The oven product was then hammer milled to liberate thebacking residue from the face fiber. Face fiber was separated from thebulk of the backing residue by screening. The yield of face fiber wasabout 41 wt%.

We note that the foregoing examples used different types of carpet asfeed, and the amount of recoverable fiber will vary from carpet tocarpet depending, for example, on the thickness of the pile.

We claim:
 1. A process for recovering face fiber material from a carpetthat includes a face fiber material and a backing material, the processcomprising: a) heating the carpet to a temperature lower than themelting point of the face fiber material, but higher than the thermaldecomposition temperature of the backing material, for a time and at atemperature sufficient to thermally decompose at least a portion of thebacking material, rendering the backing material friable; and b)applying mechanical force to the carpet so as to liberate the face fibermaterial from the friable backing material.
 2. The process of claim 1,wherein the carpet is heated in step a) to a temperature from about 175°C. to about 260° C.
 3. The process of claim 1, wherein the face fibermaterial comprises nylon 6, and wherein the carpet is heated in step a)to a temperature from 175° C. to 215° C.
 4. The process of claim 1,wherein the face fiber material comprises Nylon 66, and wherein thecarpet is heated in step a) to a temperature from 175° C. to 245° C. 5.The process of claim 1, wherein the face fiber material comprisespolyethylene terephthalate, and wherein the carpet is heated in step a)to a temperature from 175° C. to 260° C.
 6. The process of claim 1,wherein the carpet is heated in step a) for a time from about 0.1 minuteto about 120 minutes.
 7. The process of claim 1, wherein steps a) and b)are carried out in the same apparatus.
 8. The process of claim 1,wherein steps a) and b) are carried out sequentially.
 9. The process ofclaim 1, wherein steps a) and b) are carried out simultaneously.
 10. Theprocess of claim 1, wherein steps a) and b) are carried out in acontinuous process.
 11. The process of claim 1, wherein the carpet iscooled between steps a) and b) causing at least a portion of the backingmaterial to spontaneously fracture.
 12. The process of claim, 1 whereinthe face fiber material comprises a polyester.
 13. The process of claim1, wherein the face fiber material comprises a polyamide.
 14. Theprocess of claim 1, wherein the backing material comprises a polyolefin.15. The process of claim 1, wherein the backing material comprises anatural fiber.
 16. Face fiber material recovered according to theprocess of claim
 1. 17. An extruded article comprising the face fibermaterial of claim
 16. 18. An injection-molded article comprising theface fiber material of claim
 16. 19. The process of claim 1, furthercomprising chemically recycling the face fiber material.
 20. The processof claim 1, further comprising separating any inorganic filler from thefriable backing material.
 21. The inorganic filler separated accordingto the process of claim
 20. 22. A process for recovering face fibermaterial from a carpet that includes a face fiber material and a backingmaterial of different chemical composition than the face fiber material,the process comprising: a) heating the carpet to a temperature lowerthan the melting point of the face fiber material, but higher than theinitial thermal decomposition temperature of the backing material, for atime and at a temperature sufficient to thermally decompose and/oroxidize at least a portion of the backing material, rendering thebacking material more friable than the untreated backing; b) applyingmechanical force to the carpet so as to liberate the face fiber materialfrom the friable backing material; and c) removing any contaminants fromthe face fiber material through one or more mechanical means.
 23. Thefriable backing material recovered according to the process of claim 22.24. A desulfurization agent comprising the friable backing materialrecovered according to the process of claim
 22. 25. A method ofseparating at least a first type and a second type of fibers that areentangled, the process comprising: a) heating the entangled fibers to atemperature lower than the melting point of the first type of fiber, buthigher than the thermal decomposition temperature of the second type offiber, for a time and at a temperature sufficient to thermally decomposeat least a portion of the second type of fiber, rendering the fibers ofthe second type of fiber friable; and b) applying mechanical force tothe entangled fibers so as to liberate the first type of fiber from thefriable second type of fiber.